For bacon cake from the baking tray first boil salt potatoes, drain and let cool. For the dough of bacon cake rye flour and wheat flour mix. Dissolve fresh yeast in lukewarm water. Knead the yeast, sugar and salt into the flour. Cover and leave to rise in a warm place for 30 minutes. Preheat baking oven to 250° C. Roll out the dough round on a floured work surface. Form a small edge. Place the dough on a baking tray lined with baking paper. For the topping, crush the potatoes. Stir in egg and sour cream. Season with salt and pepper. Spread over the dough. Cut leeks into rings. Dice the bacon and sauté in oil. Add leeks. Briefly sauté. Sprinkle leek and bacon over the cake. Bake the bacon cake from the baking tray on the lowest rack for 25 minutes. Serve the baking sheet cake warm.